SEPARATION OF NOBLE-METALS (LEAD AND GOLD ) FROM A GEOLOGICAL MATRIX BY ION-EXCHANGE CHROMATOGRAPHY AND X-RAY-FLUORESCENCE SPECTROMETRY

A relatively rapid and simple procedure to determine gold and platinum in various geological samples is described. The sample first is diges ted by aqua regia; dissolved gold and platinum are adsorbed on a stron gly basic anion-exchange membrane filter according to the batching mod e from dilute HCl media. Analysis were performed directly on membrane filter by wavelength dispersive X-ray fluorescence spectrometry (WD-XR F). Repeated cycle countings strategy is employed to improve precision and the limit of determination. We demonstrate than aproximatively 35 eta g of metal adsorbed on membrane filter is the smallest quantity o f gold or platinum mesurable. The procedure extend to bismuth and thal lium which quantitatively accompanie noble metals during the separatio n and collection scheme. The procedure is evaluated by measuring the c oncentration of these elements in some geochemical reference standards and compared with published values. Recovery is in all cases comprise between 80 to 100%.